The present invention relates to a method for providing the inner surface of pipe lines, chiefly those already laid under the ground, for example, such as gas conduits, city water pipes and pipes enclosing power transmission wires or telephone cables, with a lining with a view toward reinforcing the pipe lines or repairing damaged portions thereof. More particularly, the present invention is directed to a method for providing the inner surface of a pipe line with a flexible lining material by turning a tubular lining material inside out through the action of a pressurized fluid, wherein the inner surface of the pipe line containing the flexible lining material is heated with a gaseous fluid ejected through pores formed in a tube which is introduced into the interior of the pipe line.
When a pipe line as described above is provided with a lining, it has been the practice to apply a flexible lining material onto the inner surface of the pipe line by means of a binder. In this case, since the lining material is to be attached together with an air-tight pipe, a binder containing a volatile component cannot be used. For this reason, two-component, reaction curing type binders, such as epoxy resin binders, are generally utilized. However, when using such binders, they should not start to harden in the course of the lining operation, so that binders with a fairly long pot life have to be utilized, thereby taking into account the time required from their preparation, to completion of evagination and insertion of the lining material. On the other hand, the longer the pot life of a binder, the longer is its curing time in approximately equal proportion thereto. Therefore, using such binders, the bonding between the lining material and the inner surface of the pipe line will takes a longer time.
It is known that warming an adhesive, a binding agent, accelerates its hardening, thus reducing its curing time. For instance, when a binder having a pot life of 3 hours at 20.degree. C. is warmed up to 60.degree. C., it starts to harden within about 10-20 minutes and its hardening can be nearly completed within about 30 minutes to 1 hour. Accordingly, if the pipe line could be adequately warmed over its full length, the hardening of the binder could be accelerated leading to a reduction in the time required for lining the pipe, which is very desirable. However, it is extremely difficult to uniformly warm an underground pipe line over its entire length, extending sometimes for several hundred meters. Though it is a common practice to warm the binder by introducing a heating medium into the lining material which is firmly attached to the inner surface of the pipe line, there is no available heating medium which is completely suitable for this purpose. For example, even if a hot blast of a gas is introduced into the pipe, the treatment has to be continued for a long period of time, e.g. hours, in order to warm the pipe line over its entire length because of the small heat capacity of the hot blast. This approach is almost impossible and thus impractical. Moreover, while direct introduction of pressurized steam is also conceivable, it remains extremely difficult to control temperature of the steam. Thus a temperature of the steam of 100.degree. C. or higher around the inlet of the pipe can subject the lining material to the effects of moisture as well as heat which may result in the eventual intense deterioration of the lining material. In addition, although warm water may also be introduced into the pipe, a large quantity of water would be required for uniformly warming a long section of pipe line. Also, it would not be easy to drain this large quantity of water which is introduced after the hardening of the adhesive agent.
Another approach has been to incorporate an electroconductive heating element in the pipe line itself or the lining material. However, this method not only is expensive but also requires the heating element to be incorporated at the time of laying the pipe line. Also this is not feasible with respect to a pipe line that is already buried. In any event, once the conductive heating element has broken down within the pipe line, this method can no longer be utilized.
No pertinent prior art is known for internally warming a lining material applied to the inner surface of a pipe line to accelerate the curing of a resinous binder to thereby shorten the time required for lining a pipe line. U.S. Pat. No. 4,064,211 shows in column 4, lines 2-6, the use of a circulation pipe 46 for controlling the temperature of water contained within a lining tube. This patent appears to suggest heating a lining material internally with hot water introduced into the tube. According to the method disclosed in this patent, however, that portion of the tube near one end of the pipe line through which the hot water has been introduced experiences localized overheating and the temperature drops as the distance from this end becomes larger. As an additional disadvantage, a large amount of hot water and a large heat source are required for conducting this method. Thus, expensive facilities are necessary in this method if an outdoor operation is carried out, for example, for lining underground pipe lines.
Accordingly, an object of the present invention is to provide a method for effectively lining pipe lines, particularly underground pipe line;
Another object of the present invention is to provide a method and apparatus for accelerating the hardening of a binder by adequately and uniformly warming a pipe line over its entire length;
A further object of the present invention is to provide a method and apparatus for shortening the time required for lining pipe lines;
Still another object of the present invention is to provide a means for internally and uniformly heating the lining material of a pipe line;
Yet another object of the present invention is to provide an inexpensive method and apparatus for lining a pipe line; and
A still further object of the present invention is to provide an effective method and apparatus for lining a pipe line by combining the steps of evagination and internally heating.
Further scope of applicability of the present invention will become apparent from the detailed description given hereinafter. However, it should be understood that the detailed description and specific examples, while indicating preferred embodiments of the invention, are given by way of illustration only, since various changes and modifications within the spirit and scope of the invention will become apparent to those skilled in the art from this detailed description.
Pursuant to the present invention the above disadvantages can be eliminated and the objects of the present invention can be achieved by treating a tubular lining material which has been applied to the inner surface of a pipe line with a heated gaseous medium, for example pressurized steam, which is ejected through pores, including micropores, which are formed in a tube which is introduced into the interior of the pipe line. The heated gaseous medium functions to uniformily accelerate the curing of a resinous binder material used to attach the tubular lining material to the inner surface of the pipe line, thereby shortening the time required for the completion of the lining treatment.
The method and apparatus for uniformily accelerating the curing of the resinous binder as defined by the present invention is applicable to any method which might be used for lining a pipe line with a tubular lining material but is particularly applicable to the lining method and apparatus of U.S. patent application Ser. No. 107,870 wherein the present curing method is combined with the evagination system disclosed therein. FIGS. 3 to 6 of the present application also show the evagination method and apparatus for lining pipe lines combined with the curing method and apparatus of the present invention.